Digital and conventional techniques for dental, panoramic and intraoral radiography, were compared to assess measurement accuracy. The study was carried out on two plastic models of maxillary and mandibular arches, each containing 14 teeth extracted and positioned in their anatomical site. The teeth were prepared by opening the pulpal cavity and inserting endodontic wires within the canals. Intraoral x-ray images were taken with long-cone technique using a commercial high-resolution film and with a charge coupled device (CCD) sensor (radiovisiography). The models were then submitted to panoramic tomography with photostimulable phosphor plates. The length of the canals was measured on each image and compared to the length of the inserted wires. For the digital pictures, the measurement was performed directly on the monitor with the aid of electronic calipers. Magnification averages 3.40%, 9.47% and 14.11% for anterior teeth in intraoral radiography, in radiovisiography and panoramic radiography, respectively. The results demonstrate the presence of some degree of magnification for every radiographic procedure. This effect becomes statistically significant for both radiovisiography and digital panoramic techniques, especially in the latter. In spite of their well-known practical and dosimetric advantages, digital techniques in dental radiology must be used carefully whenever a reliable measurement is required.